ANATOMYRESEARCHSEGMENTSUMMARY The overarching goal of neuroanatomy is to establish a structural framework to integrate multiscale and multi-modalinformationandtoprovidearoadmapthatguidestheexplorationofneuraldynamicsandbrain function. ?Anatomic? neuron types can be described by their location, morphology, and connectivity. As morphologyisoneofthemostintuitivedepictionsofcelltypesthatreflectstheirinput-outputconnectivity,the visualization, characterization and quantification of their complete and detailed shapes are key to the identification and classification of anatomic neuron types. However, these have remained enduring challengesforoveracentury,asmostvertebrateneuronsaresimultaneouslysmallandlarge,spanningvast spatialscalesfromsubmicrontocentimeter(e.g.corticospinalneuronsconnectingcortextospinalcord).The overallgoalsoftheAnatomySegmentareto:1)establishaForebrainProjectionCellAtlasthatintegrates in-depthmulti-modalityanatomicandmolecularinformationacrosscerebralcortex,basalganglia,thalamus, and hypothalamus. A forebrain projection neuron atlas will provide a core skeleton that anchors nearly all other brain structures and the transcriptome cell atlas constructed in the Molecular Segment;? 2) advance current and emerging imaging technologies and pipelines with improved resolution, throughput and lower cost. We will use several state-of-the-art imaging technologies and pipelines to obtain multi-modal, high- resolution whole brain datasets on cell location, morphology, projection, and connectivity of vast sets of forebrain neurons, all registered in the mouse brain Common Coordinate Framework (CCF). To achieve high-resolution brain-wide imaging, we will use 1) Serial Two-Photon tomography (STP) to image marker- defined neuronal body distribution, 2) STP to image axon projection patterns of genetic and virally-labeled neuron subpopulations, 3) fluorescence Micro-Optical Sectioning Tomography (fMOST) to image and reconstruct the complete morphology of single neurons ? the ultimate resolution for anatomic cell typing. Importantly, this anatomical forebrain atlas will integrate single-cell molecular information collected and positionally mapped for the same cell types in the Molecular Segment, towards a close-to-completion MolecularandAnatomicalatlasofthemouseforebrain.